A high-speed portable Internet (HPi) system employs the orthogonal frequency division multiplexing (OFDM) for modulation/demodulation and the frequency division multiple access (FDMA)/time division multiple access (TDMA) for user multiplexing. Such an HPi system has a base station (BS) as a coordinator that manages and schedules a bandwidth. Thus, when a mobile terminal requests the BS to allocate a bandwidth for data transmission, the BS allocates the corresponding bandwidth and the mobile terminal transmits data using the allocated bandwidth.
Methods for requesting a bandwidth include a basic access request and a random access request. The basic access request is not a contention-based request, and thus the mobile terminal piggybacks the data on a unicast-based bandwidth or a leftover bandwidth within a given bandwidth in response to polling of the BS. However, the random access request is a contention-based request and thus multiple users request bandwidth allocation by competing with each other for one dedicated channel.
Uplink traffic is classified into four service classes: an unsolicited grant service (UGS), a real time polling service (RTPS), a non real time polling service (NRTPS), and a best effort (BE). The UGS is designated, for periodic transmission of fixed size data such as the voice over Internet Protocol (VoIP), the RTPS for periodic transmission of variable size data such as the motion picture experts group (MPEG) video, the NRTPS for period transmission of variable data bursts (i.e., the file transfer protocol (FTP)), and the BE for traffic having lower priority such as mailing and web-browsing.
The above-noted service classes establish connections between the mobile terminal and the BS by applying QoS parameters such as delay, jitter, error rate, and so on. The connections may be varied depending on the QoS parameters, and each connection is defined by a connection identifier (CID).
When the mobile terminal receives a packet transmission request from an application program to request a bandwidth from the BS, and the BS grants an available bandwidth so that the mobile terminal may guarantee the bandwidth. The mobile terminal then transmits the packet through the granted bandwidth.
In the bandwidth request/grant, the BS receives bandwidth allocation requests form the mobile terminal for each connection, but allocates bandwidths to all the mobile terminals in order to overcome the problem in which the BS fails to control the case in which the mobile terminal continuously generates traffic when the BS receives the bandwidth request and allocates bandwidth to the mobile terminal.
The mobile terminal performs a different operation according to a QoS characteristic of the established connection when requesting a bandwidth from the BS and using the same.
User packets of the mobile terminal are classified into four service classes and stored therein. The mobile terminal requests the bandwidth for the stored packets from the BS, and transmits the stored packets according to a priority-based QoS policy when guaranteeing the bandwidth.
Uplink data includes a management message in addition to the user packets. When a bandwidth is requested and then guaranteed, the management message is transmitted therethrough. The management message is classified into a basic/primary CH class and a secondary CH class according to attributes of the management messages. The basic CH class has the highest priority and the secondary CH class has the lowest priority.
Similar to the way of transmitting the user packets, the management message is classified into three services and stored in the mobile terminal when management message transmission is requested. When the bandwidth requested to the BS for transmitting the stored management messages is guaranteed, the stored management messages are transmitted according to the priority-based QoS policy.
When both of the management message and the user packet are stored in the mobile terminal, the management message is transmitted with, priority higher than the user packet since the management message is a control message related to operation of the HPi system and is thus more important than the user packet.
As a prior art, a medium access control (MAC) device in a network system employing division multiplexing has been disclosed in the Korean Patent Application No. 10-2001-63665 filed on Oct. 16, 2001 (entitled “Media access control device with QoS of a network system introducing a way of wavelength division multiplexing”).
In more detail, the MAC device includes: a packet receiver exclusively receiving packets that are sequentially flowing to a temporary node through mini slots, and selectively storing/outputting the corresponding packet according to destined nodes; a packet transmitter transmitting a sequence of packets to be transmitted using the mini slots passed via the packet receiver; a queue storing the sequence of packets; a priority-based queue temporarily storing a specific packet selected by, the packet receiver; and a queue manager prioritizing data in the queue storing the packets to be received and in the priority-based queue, and controlling the packet transmitter to transmit the data in a prioritized order. The disclosed invention also provides, a priority managing structure to manage data transmission by comparing priority between the data temporality stored in the queue and the data stored in the priority-based queue to thereby prevent transmission delay of data having lower priority and simultaneous data transmission (data collision) with other stations.
As another prior art, the U.S. Pat. No. 6,640,248 filed on Jul. 9, 1999 discloses “Application-aware, quality of service (QoS) sensitive, media access control (MAC) layer”.
In more detail, the prior art provides an application-aware resource allocator to specify application programs sensitive to IP Flows (Transmission Control Protocol Flow, and User Datagram Protocol Flow), allocate the corresponding resource, analyze a header of a start packet of each flow, and distinguish characteristics of each application program to thereby control QoS in consideration of the characteristics of the application programs.
In addition, the U.S. Pat. No. 6,104,700 filed on Feb. 3, 1998 discloses “Policy based quality of Service.” This invention is related to a method for controlling a policy based quality of service for managing, monitoring, and prioritizing traffic within a network.
In more detail, the foregoing invention selectively transmits data packets by using a traffic group generated when receiving the packet so as to flexibly control priority-based QoS policy for dynamic bandwidth allocation.
However, in a conventional portable Internet system, the mobile terminal cannot efficiently transmit uplink data because a queue for user packet/management message, bandwidth allocation for the user packet/management message, and data transmission based on priority of the QoS are not properly managed.